1. Field of the Invention
This invention relates to novel tetrahydrocarbyl phosphonium phenoxide salts and the preparation of new epoxy-containing materials by a process employing these and other salts as catalysts. In one preferred embodiment, this invention pertains to a process for making a linear, polymeric material having a molecular weight of at least about 100,000 from the advancement reaction of an epoxy resin with a polyhydric phenol (specifically bisphenol A) in the presence of a tetrahydrocarbyl phosphonium bisphenoxide salt.
This invention also relates to precatalyzed epoxy resins and precatalyzed polyhydric phenolic compositions comprising, respectively, an epoxy resin having an average of more than one vicinal epoxide group per molecule or a polyhydric phenol, each composition containing a tetrahydrocarbyl phosphonium phenoxide salt catalyst for promoting the reaction between an epoxide and a phenolic hydroxyl group.
2. Prior Art
It is well-known in the art to produce hydroxyl-containing ethers by reacting a vicinal epoxide with a compound bearing phenolic hydroxyls in the presence of such catalysts as tertiary amines, quaternary ammonium halides, phosphonium halides and the like. See, for example: U.S. Pat. Nos. 2,216,099; 2,633,458; 2,658,855; 3,377,406; 3,477,990; 3,547,881; 3,547,885; 3,694,407; 3,738,862; 3,948,855; and 4,048,141. Canadian Pat. No. 893,191, German Pat. DT Nos. 2,206,218 and 2,335,199 and the text, Handbook of Epoxy Resins by H. Lee and K. Neville, McGraw-Hill (1967), Epoxy Resins-Chemistry and Technology, Edited by C. Maynard and Y. Tanaka, Marcel-Dekker, Inc. (1973) are also of interest. It is also taught in U.S. Pat. No. 4,048,141 that certain phosphonium catalysts promote the reaction between vicinal epoxides and phenols and/or carboxylic acids or anhydrides.
The prior art catalysts for promoting reactions of epoxides with phenols have generally been deficient in one or more aspects. In many instances, the catalysts react with the epoxy reactant and thus preclude the marketing of a blend comprising an epoxy resin and a catalyst, a so-called "precatalyzed epoxy resin". Blends comprising a polyhydric phenol and a catalyst (i.e., a precatalyzed polyhydric phenol) have likewise been avoided due to possible adverse reactions of the two components. Many prior art catalysts exhibit a lack of selectivity in that they simultaneously promote the reaction of an epoxy resin with both the phenolic hydroxyl group(s) on the reactant and the aliphatic hydroxyl group(s) on the product, which produces branched or cross-linked polymers rather than the desired linear polymers. In still other instances, the reaction rate is unsatisfactory and/or the product is highly colored or contaminated with corrosive anions (e.g., chloride). Moreover, vinyl ester resins made from the catalyzed reaction products of epoxy resins and polyhydric phenols in the presence of most prior art catalysts require undesirably long cure times because of the presence of relatively high concentrations of phenolic hydroxyl groups.
The prior art catalysts, to a greater or lesser degree, produce at best linear or substantially linear polymers of relatively limited molecular weights. For example, the advancement reaction of 4,4'-isopropylidenediphenol (i.e., bisphenol A) with a diglycidyl ether of bisphenol A in the presence of a triphenyl ethyl phosphonium acetate salt-acetic acid complex even when followed by further reaction with tetrabromobisphenol A produces a linear polymer with a maximum weight average molecular weight of about 60,000 as determined by gel permeation chromatography. These deficiencies have now been remedied by the subject invention.